In recent years, LEDs are widely used to replace the conventional tungsten light bulbs in many lighting and signing applications because of the high luminance efficiency. However, as the current LED manufacturing process uses the semiconductor epitaxial process, the opto-characteristics of the LEDs vary greatly from batches to batches. Therefore, it is necessary to calibrate the manufactured LEDs. The current calibration method is to use a complex control circuit to obtain and store the optimal calibration data for each LED in the memory so as to calibrate the image signal in real-time and improve the lighting uniformity of the LEDs.
FIG. 1 shows a schematic view of a conventional LED calibration system. As shown in FIG. 1, a calibration host 20 outputs calibration control signal CCT, image enabling signal CCPG and image capturing control signal CCPT to LED module 10, image pattern generator 30 and image capturing device 40, respectively. According to CCT, LED module 10 enters either calibration mode or normal display mode. Image pattern generator 30, based on CCPG, generates image pattern signal PGS. Image capturing device 40, based on CCPT, performs image capturing on light LT emitted from LED module 10, and generates image capturing data IDT for calibration host 20. Calibration host 20 receives and processes IDT to generate calibration data for LED module 10, and LED module 10 stores the calibration data.
LED module 10 includes a controller 12, a driver 14, a memory 16 and a plurality of LED arrays 18, where each LED array 18 further includes a plurality of LEDs. When LED module 10 enters the calibration mode, controller 12 receives PGS to generate driver control signal DRVCTL for driver 14. After receiving DRVCTL, driver 14 generates drive signal DRV to drive the LEDs of LED array 18 to emit light LT of required brightness and color. At the same time, controller 12 receives CCT from image capturing device 40, and stores calibration data CCDT of CCT in memory 16 so that controller 12 can make all the LEDS generate uniform light by capturing CCDT in memory 16 to calibrate DRVCTL when LED module 10 enters the normal display mode.
The shortcomings of the conventional technology are the difficulty to install the above complex calibration device in the small-sized LED lighting device with the limited circuit board area and the increasing number of the LEDs, and the additional cost of the calibration device incurred to counteract the market competiveness.
Another shortcoming of the conventional technology is that the calibration data of all the LEDs are stored in a single memory of the module. If a few LED malfunction, it is necessary to perform calibration and obtain all the LEDs' calibration data of the new module after the replacement of the malfunctioned LEDs. However, for outdoor LED display, this approach increases the maintenance cost and sometimes even the entire LED module needs to be replaced.
Therefore, it is imperative to devise an easy-to-maintain and simply-structured LED module and a more efficient LED calibration method and system so improve the calibration of LED modules without increasing the manufacturing cost.